There are demands for improvement of reliability from the viewpoint of prevention of failure occurrence during traveling of a vehicle and improvement of an output torque from the viewpoint of weight reduction of the vehicle in hybrid cars and electric cars. Three-phase six-wire type driving devices have been considered in response to such demands, but there is a problem that a 3n-order harmonic current is superimposed on a drive current for driving an electric motor and a loss such as a copper loss increases because the electric motor to which a neutral point is not connected is used.
One of background art in this technical field is JP 2004-80975 A (PTL 1). In this publication, it is described that “a 3n-order harmonic voltage command value for canceling a 3n-order harmonic current (3 is the number of phases, n is an integer) included in a drive current for driving an electric motor is calculated, and a three-phase voltage command value is corrected”. Accordingly, a target voltage is corrected so as to cancel the 3n-order harmonic current, and thus, it is possible to the harmonic current in the drive current and to reduce the loss caused by the harmonic current.